Analog Bar Graph Application; Using The Analog Bar Graph - Fluke 27 User Manual

High-voltage stacked diode assemblies can usually be
tested for forward and reverse resistance changes using
conductance. These assemblies typically have such high
forward voltage drops that the diode test or resistance
modes cannot test them.

Analog Bar Graph Application

In looking at the analog bar graph, notice that it is
composed of segments that simulate an analog needle.
The bar graph performs the same function as an analog
meter needle, but it eliminates the mechanical overshoot
inherent in needle movements.
A negative (-) annunciator is displayed at the left end of
the bar graph when taking a reverse polarity dc
measurement. Assume that a slowly varying dc voltage is
the input signal. As the input goes more positive (from
zero), a bar graph segment is displayed, and additional
segments are displayed from left to right, to indicate the
input level as it increases. Now, assume that the input
level slowly decreases. Fewer bar graph segments are
displayed as the signal decreases, then the - annunicator
flashes as the signal level passes through 0. As the
signal goes more negative, the - annunciator is displayed
from left to right, indicating a more negative input signal.
The first segment is an indication greater than or equal to
20 counts.
Note that every fifth segment of the bar graph is slightly
larger than those in between, and every tenth segment is
larger yet. These larger segments provide a quick
reference for bar graph indications. The largest segments
(every 10th segment) divide the display into thirds. Thus,
if the bar graph indicates 11 segments on the 32.00V
range, the input voltage is 10 to 11 volts; if the bar graph
indicates 11 segments on the 320.0V range, the input
voltage is 100 to 110 volts. If the input equals or exceeds
3000 counts on the range selected, the bar graph
displays, an arrow at the far right of the display. If the
manual range annunciator (R) is not displayed, the Fluke
27 automatically switches to the next high range if the
input exceeds approximately 3260 counts

Using the Analog Bar Graph

The analog bar graph is most useful in making
adjustments and performing limited diagnostics. Bar
graph response is fast and precise, so it can be used to
easily reach a setting within a few percent of the final
adjustment. The bar graph can be used to make rough
adjustments quickly; then the 3200-count digital display
can be used for final adjustment.
The analog bar graph is useful for performing limited
diagnostics in applications were rapidly fluctuating signal
levels cause the flashing digits of a digital display to be
useless. Like the traditional VOM needle, the analog bar
Analog Bar Graph Application
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